| Abstrakt: |
Reaction of the dibenzyl sulfide complex [(η5-C5H5)Re(NO)(PPh3)(S(CH2Ph)2)]+TfO- (4a+TfO-) and t-BuOK (THF, −80 °C) gives the thiolate (η5-C5H5)Re(NO)(PPh3)(SCH(o-C6H4CH3)Ph) (5a; 99%) as a 96:4 mixture of SR,RS/SS,RR Re:C diastereomers. This transformation involves initial deprotonation of a benzyl group to give an ylide, followed by [2,3]- and [1,3]-rearrangements. A crystal structure of (SR,RS)-5a establishes the configuration. Similar reactions of the benzyl allyl sulfide complexes [(η5-C5H5)Re(NO)(PPh3)(S(CH2CR&dbd;CH2)CH2Ph)]+TfO- (R = H, CH3) give mainly the thiolates (SS,RR)-(η5-C5H5)Re(NO)(PPh3)(SCH(CH2CR&dbd;CH2)Ph), derived from benzyl group deprotonation. Some thiolates derived from allyl group deprotonation also form. Similar reactions of the allyl β-keto sulfide complexes [(η5-C5R5)Re(NO)(PPh3)(S(CH2CR&dbd;CR2)CH2COPh)]+X- (R/R/R = H/H/H, H/H/CH3, H/CH3/H, CH3/H/H) give the thiolates (η5-C5R5)Re(NO)(PPh3)(SCH(CR2CR&dbd;CH2)COPh), derived from CH2COPh group deprotonation, as >96:<4 to 68:32 diastereomer mixtures. Reactions of 4a+TfO- with MeLi give mainly the [1,2]-rearrangement product (η5-C5H5)Re(NO)(PPh3)(SCH(CH2Ph)Ph) ((35−70):(65−30) diastereomer mixtures), which has been independently synthesized. The thiolate ligands are easily converted to free methyl sulfides. Mechanisms of diastereoselection, and similar reactions of organic sulfonium salts, are discussed. |
